IPK, preware and touchpad ???

I just want to know if there's a way to "un-associate" ipk file with preware....
I explain myself.... I've tried to download an app from a site, like mediafire, but when I hit the download button, instead of downloading the app into my download folder, it try to open it with preware.

I choose to associate ipk file with preware during the first lunch of preware.... But is there a way to unassociate ipk....